Hammer bars composed of a body and of tools have proved most satisfactory because the tools have a high wear resistance and are replaceable so that such bars have a stron cleaving action and a lone life. These results depend on the provision of a sufficiently strong and durable joint between the tools and the body. For this purpose, as is apparent from EP-B-0 224 836, the tools are provided with one or more retaining rails, which is or are rounded in mushroom shape and slidably inserted in longitudinally extending retaining grooves formed in the body, and the retaining rail and the retaining groove have complementary cross-sectional shapes so that the tools and the body are interconnected by a positive joint, which is fracture-proof and has a high load-carrying capacity. In the operational use of such a hammer bar, dust evolved as a result of the comminuting work of the crusher will inevitably enter the gaps and cavities left between the retaining groove and the retaining rail and such clearances will eventually be completely filled with dust so that the removal and replacement of the tools will be rendered more difficult after a prolonged operation and expensive special machines, such as presses, are often required for such removal and replacement.